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Note
Offset Registers
Eight pseudo-registers (R0 through R7) called offset registers are
used to simplify the debugging of relocatable and position-
independent modules. The listing files in these types of programs
usually start at an address (normally 0) that is not the one at which
they are loaded, so it is harder to correlate addresses in the listing
with addresses in the loaded program. The offset registers solve this
problem by taking into account this difference and forcing the
display of addresses in a relative address+offset format. Offset
registers have adjustable ranges and may even have overlapping
ranges. The range for each offset register is set by two addresses:
base and top. Specifying the base and top addresses for an offset
register sets its range. In the event that an address falls in two or
more offset registers' ranges, the one that yields the least offset is
chosen.
Note
Example:
1
2
3
4
5
6
7
In commands with range specified as addr addr, and
with size option
W
(ending) address is acted on only if the second address
is a proper boundary for a word or longword,
respectively.
Relative addresses are limited to 1MB (5 digits),
regardless of the range of the closest offset register.
A portion of the listing file of an assembled, relocatable module is
shown below:
0 00000000 48E78080
0 00000004 4280
0 00000006 1018
Entering Debugger Command Lines
or
chosen, data at the second
L
*
*
MOVE STRING SUBROUTINE
*
MOVESTR
MOVEM.LD0/A0,—(A7)
CLR.LD0
MOVE.B(A0)+,D0
4
4-7
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